The present invention generally relates to oil burners both for light and heavy heating oils and of the type which comprises a burner housing including several burner nozzles which are fed with pressurized oil, and which burner housing combustion air is blown and is mixed with the finely distributed oil drops which are ejected from the burner nozzles thereby providing a fuel-air mixture. The invention specifically has been developed in connection to oil burners the heating capacity of which can be controlled from full capacity down to a predetermined low heating capacity, but the invention is not restricted to this technical field but may be utilized in all available types of oil burners having several burner nozzles.
Burners having several burner nozzles are previously known. In such burners the nozzles are mounted in a nozzle carrier which in turn is mounted inside a cup in which the oil drops are mixed with incoming air and in which the fuel-air mixture is inflamed at or close to the outlet of said mixture cup. In the previously known burners having several nozzles the said nozzles generally are mounted with the oil jet axis extending axially in relation to the mixture cup so that the oil from all nozzles provide a body of oil drops flowing out of the mixture cup with the periphery of the body of oil drops substantially in contact with the opening of the mixture cup. Such an apparatus works well when operating at full capacity and on a slight reduction of capacity. The best fuel economics and the best operation conditions and the lowest CO-content is obtained if the burner is allowed to operate continuously and with an exactly predetermined mixture of oil and air. When reducing the heat capacity, for instance at hot ambient temperature like in the summer it may be necessary to shut one or more of the burner nozzles to obtain a sufficiently low heating capacity. Since the burner nozzles are mounted as centrally but with the burner axis directed axially the fuel body thereby is placed as centrally in relation to the mixture cup or flame cup and the oil drop body therefore does not fill up said outlet. Further some portion of the introduced combustion air passes the outlet of the flame cup without being mixed with the oil mist and therefore generally a long relationship between air and fuel of the fuel-air mixture is obtained.
The oil burners of the above mentioned type which are known today further are disadvantageous in that a total set value combustion cannot be obtained, possibly depending on an imperfect or unfavourable mixture of the oil mist from the different burner nozzles or that the jets from the different nozzled adversely act on each other. Residues of hydrocarbons and nitrous gases remain after the combustion, and non-burnt oil drops pass the flame and deposit as a fat, wet layer inside the combustion chamber and may cause the formation of carbon, choking of the burner nozzles etc.